This invention is in the field of systems for the analysis of EEG signals from the brains of human subjects.
The current state-of-the-art in workstations for processing EEG signals allows the viewing of either monopole or bipolar montages of electrode inputs. Various seizure detection algorithms have been implemented in such EEG processing workstations to help the epileptologist find epileptiform activity within hours of patient EEG data. In U.S. Pat. No. 6,016,449, Fischell et. al. describes an implantable system for the detection and responsive stimulation to stop neurological events such as epileptic seizures. The Fischell application refers to the use of a physician""s workstation for programming a separate implantable device but does not describe the use of a Physician""s Workstation as an independent system for patient diagnosis and treatment evaluation. In order for an implantable device for detecting and stopping a neurological event to operate efficiently, it is highly desirable to first determine and test the appropriate epileptiform activity detection algorithm(s) and patient specific detection parameters for each patient using an external workstation.
It is also highly desirable that the patient specific template be programmable into the implantable electrical stimulation therapy device from the workstation. In U.S. patent application Ser. No. 09/517,797, Fischell describes a processed display channel technique for patient specific seizure detection. For each patient, the processed display channel (DC) algorithm(s), detection algorithm(s) used with each PDC and best set of epileptiform activity detection parameters for the chosen detection algorithms together make up the patient specific epileptiform activity detection template. The processed display channel technique described by Fischell does not however describe a streamlined process for picking the best or optimum set of parameters. It is generally necessary to work through hours of EEG data, checking the detection parameters with each marked seizure and then going back to check for false positive detections, which is a tedious and lengthy process. It is highly desirable to provide an automated or semi-automated system that can assist the clinician in finding the optimal epileptiform activity detection algorithm for each patient.
The present invention is an epileptiform activity patient template creation system that allows the physician to efficiently develop an optimized set of patient specific parameters for one or more epileptiform activity detection algorithms. Such a template once created can be downloaded into an implantable device for seizure control. The epileptiform activity patient template creation system is primarily a computer software package that will run in conjunction with either the programming system for an implantable neuropacemaker or an EEG monitoring and analysis system such as the Physician""s Workstation (PWS) described by Fischell in U.S. Pat. No. 6,016,449. Such a workstation can be connected to patients with scalp or intracranial electrodes for acquisition of EEG data or can process previously stored EEG data collected with other EEG data acquisition systems.
Existing EEG monitoring and analysis systems allow the clinician to mark each electrographic seizure and to quickly move through the EEG data from one mark to the next. The present invention provides the additional capability to simultaneously display on a single screen a seizure data set containing all the marked seizures from one or more patient EEG files. In addition, the marked seizures in the seizure data set are time synchronized so that the seizure start mark of all the seizures are vertically aligned on the display. The present invention will work best when less than five signal channels are used for template creation. The Processed Display Channel (PDC) approach described in U.S. patent application Ser. No. 09/517,797 allows the combination of the best EEG channels into one or more PDCs.
A processed display channel (PDC) is a customized combination of specific EEG channels that best show a patient""s epileptiform activity. The advantage of processed display channel based epileptiform activity detection is that one or more detection algorithms may be run on processed signals that have been optimized to show epileptiform activity. The fundamental advantage of the optimization is to allow reduction of as many as 128 EEG channels to typically one or two PDCs.
The clinician can choose an epileptiform activity detection algorithm, manually enter a test set of template parameters, verify accurate detection of the multiple marked seizures and then have the system go back to the original EEG files to check for false positive detections.
Once all marked seizures are displayed together on a single screen, a waveform analyzer can be used to graphically show the distribution of algorithm related parameters in a selected segment of the seizure data set signals. The charts displayed can provide a guide for the manual selection of template parameters.
The present invention also has the capability to automatically find the best sets of detection parameters for multiple epileptiform activity detection algorithms and display the accuracy of the selected sets in tabular or graphical form so that the clinician can simply select the best epileptiform activity detection template created by the computer. The computer-selected template can also be adjusted and retested manually by the clinician.
It is understood that EEG is used throughout the following discussions to mean either electroencephlagram data from external scalp electrodes or electrocortigram data from intracranial electrodes. The term brain electrodes are used throughout the following discussions to mean any electrodes within or near the brain including scalp surface electrodes and intracranial electrodes. The term epileptiform activity refers to activity within the brain of a person with epilepsy that is indicative of the disease. Epileptiform activity is present during a clinical epileptic seizure but may also sometimes occur without clinical symptoms.
Thus, it is an object of this invention to provide an epileptiform activity patient template creation system that can simultaneously display a multiplicity of marked electrographic seizures.
Another object of this invention is to provide an epileptiform activity patient template creation system that can simultaneously display a multiplicity of marked electrographic seizures from two or more patient EEG files.
Still another object of this invention is to provide time synchronization of the display of the marked start of a multiplicity of electrographic seizures
Still another object of this invention is to implement a PDC based seizure detector within a physician""s workstation to provide diagnosis, template creation and testing to optimize the seizure detection means prior to implantation of an implantable electrical stimulation therapy device.
Yet another object of this invention is to provide waveform analysis tools that may be used on EEG or PDC signal segments to provide one of more histograms showing a breakdown of the signal parameters for the selected segment.
Yet another object of this invention is to provide a fully automated means to select the best set of epileptiform activity detector template parameters for a specific patient.
Still another object of this invention is to provide means to download the tested epileptiform activity detection template to an implantable electrical stimulation therapy device.
These and other objects and advantages of this invention will become apparent to a person of ordinary skill in this art upon care full reading of the detailed description of this invention including the drawings as presented herein.